What is "corruption"?
The generally-understood idea of "corruption" is when power and influence is used in immoral and exclusive ways, commonly by-passing law and socially-acceptable norms. More specifically, when most people think of "corruption" they think of bribery and brown envelopes, Swiss bank accounts and social deprivation.
These things are what existed in the toppled regimes of the "Arab Spring", and are one of the main reasons why those Arab populations finally turned their resigned frustration into vigorous revolution. It is corruption that keeps a potentially-rich country poor.
Africa is a continent rich in resources, but the wealth of those resources is only felt by the ruling elites. The DR Congo is a prime example of this: a vast nation, which contains the world's largest supply of rare metals needed for much of modern technology (such as mobile phones). On paper, DR Congo should be one of the world's richest countries, but due to corruption and malign foreign influence, it has been a war zone for the last fifteen years; Africa's "Great War".
When the corrupt ruling elite of a country ignore the law to feather their own nests, one way they stay in power is by either destroying other powerful factions, or by indulging them. In the Third World, when corrupt regimes are not killing, imprisoning or persecuting those deemed a threat, they are offering them a piece of the action. This latter form is more commonly called "cronyism". This is how Third World dictators (for example, former military leaders) keep their hold on power.
The "piece of the action", the method that the corrupt ruling elite use, is usually a system of bribery and patronage. In Third World dictatorships, government money that is given to ministers or military leaders is the prize of the ruler, an insurance for loyalty for the minister to dispose of as they wish (e.g. in a Swiss bank account). Just as important, the role also gives the individual ministers virtual omnipotence over their supposed underlings; and as such, demand loyalty in hard cash (i.e bribes). This then trickles down through the hierarchy, as each manager at each level is required to give a bribe to his relevant superior under pain of dismissal. Thus corruption and bribery runs from even the lowliest ministry clerk (who subtly demands a bribe for the most basic service to the public).
For the real reason that bribery exists in such a state is as an instrument of psychological terror. What prestige the ruler of the corrupt elite gives, he can also take away. In corrupt Third World states, a dictator offers a ministry to a favoured individual under probation; unless the dictator has special reason to fear the individual (by keeping an enemy sweet and under close watch), the newly-appointed minister knows the best way to ensure his position is to get as much money as possible from his underlings, to be used as a periodic "gift" to the leader. Thus bribery becomes a weapon of government terror; pay your dues, or risk the wrath of your superior. And "wrath" in a country without rules is simply whatever the person in influence is capable of.
This is the primer in "corruption". The West has generally been free of large-scale corruption for the last hundred years or more, depending on how wide your definition is. But, as I said at the start, what is "corruption"?
Corruption has never really left some aspects of Western society; it simply became more refined. I wrote before about Britain's establishment here, and the link between corruption and incompetence. In the Third World, corruption is a cancer that infects every level of society, as explained above. Corruption no longer infects every level of Western society; rather, corruption is something that only the richest can afford.
In the Third World, corruption is almost egalitarian in how is spread through every level of society. In Africa, if you pay the bribe the right person, you can get what you want. In the West, corruption is a luxury good: only the richest can afford the fees.
Consider the number of scandals - be it banking practices, tax scams - that cost the UK government billions in revenue. The money lost through these corrupt practices of the elite dwarf into insignificance the petty fraud carried-out the "benefit cheats" widely-reported in the media. But it is easier for the government to target those at the low end of society for persecution. This is a practice right out of a corrupt Third World dictators' handbook. When the Conservative government feels challenged, rather than tackle the corrupt system and those individuals considered part of the British "establishment", it isolates those who it sees as an easy target - the petty fraudsters at the lowest end of the social spectrum.
Ian Duncan Smith is another example of the Conservatives' instinct for "divide and rule" tactics. For those with the least to lose and most to gain from social revolution, it is in the elite's interest to ensure they are as divided as possible: Osborne's "strivers versus skivers" is another variation on the same theme. Whether this is by design or (more likely) a combination of education and gut instinct, people like the Conservatives have a vested interest in "the system": the British "establishment" that has raised them, therefore they fear anything that threatens change.
"Divide and rule" is how corrupt elites stay in power, from Africa to the UK. Corruption kills societies because it breeds incompetence and inefficiency. When there is no rational oversight, and when everything is influenced by not what you know, but who you know or how much money can buy you influence, intelligence becomes irrelevant.
One important reason why the financial crisis happened is because those in positions of responsibility in the finance sector failed to ask questions. As long as the system generated money, they didn't ask why things worked. In the end, the system crashed because no-one knew how anything really worked. No-one has realised that the system they relied on was a fraud, literally. Everyone was defrauding everyone else, but no-one thought this was wrong - it was normal at the time.
This is exactly the same psychology that exists in corrupt Third World states. When everyone around you is corrupt, it no longer seems like corruption: it seems normal.
Back to the financial crisis, because those in positions of responsibility all had similar educations, were from the similar backgrounds, often had known each other's families for years, they had all progressed to their positions of authority thanks to the same corrupt system. Therefore, they assumed that they knew what they were doing simply because of their backgrounds. David Cameron and George Osborne share the same deluded psychology.
Corruption therefore breeds incompetence because people do not gain power through meritocratic ability, but through influence or other means. Thus you have people who are put in positions of power far beyond their ability. And as they delude themselves into thinking they have attained power fairly, they are more likely to become vain and arrogant, haughty and over-bearing. As living proof of this, a number of Conservative ministers seem to fit into this personality set. Worse, such a corrupt system makes these incompetent people make mistakes, and they naturally react by persecuting those they feel most threatened by once their mistakes have been discovered. Thus corruption is an evil of society: it breeds on amorality, it disregards intelligent thinking and efficiency, it rewards incompetence, and punishes all those who seek to change the status quo.
In this way, a corrupt society is a morally evil one, too. The process of moral degradation as described above as much describes what happens when you put psychopaths in positions of power. This also explains why psychopaths thrive in corrupt societies, and why there are likely to be a disproportionately-high number of psychopaths in corrupt societies.
Psychopaths are products of childhood chaos, and thrive on social chaos. And corruption, by definition, creates chaos.